Abstract
This study has identified IgG and IgM anticoagulant antibodies in the synovial membranes of patients suffering from haemophilia and rheumatoid arthritis (RA) but not in synovial tissues from normal subjects or in patients with other arthritides. In the majority of cases the antibody appeared to have the specificity of the lupus-like anticoagulant (LLA) seen in patients with systemic lupus erythematosus (SLE). The importance of these findings with regard to the treatment of certain cases of haemophilia and RA and the possible relation between the presence of these antibodies and viral infections is discussed.